Ophthalmologic apparatus

ABSTRACT

An ophthalmologic apparatus of some exemplary embodiments includes an illumination system, interference photographing system, anterior eye segment photographing system, first optical path coupling element, and controller. The illumination system projects illumination light output from a light source, onto the anterior eye segment of a subject&#39;s eye. The interference photographing system performs photographing of an interference pattern formed on the cornea by the illumination light. The anterior eye segment photographing system performs photographing of the anterior eye segment onto which the illumination light is being projected. The first optical path coupling element couples the optical path of the interference photographing system and the optical path of the anterior eye segment photographing system with one another. The controller controls a display device to display an interference image acquired by the interference photographing system, over an anterior eye segment image acquired by the anterior eye segment photographing system.

FIELD

The present invention relates to an ophthalmologic apparatus forexamining the state of tears of a subject's eye.

BACKGROUND

In recent years, patients with dry eye syndrome are increasing. Thecauses of this are believed to be abusing of eyes due to work performedusing a display of a computer or the like (VDT work), drying of air bycooling and/or heating, wearing of a contact lens, and the like.

The most common method of testing for dry eye syndrome is the Schirmertest, which measures the amount of tears. In addition, observation ofthe cornea stained with fluorescein using a slit lamp microscope and anexamination for measuring the stability of the tear film (tear filmbreakup time (BUT) examination) are also being employed.

The followings are known apparatuses for examining dry eye syndrome.Japanese Unexamined Patent Application Publication No. 1997-289970discloses an ophthalmologic apparatus in which a light projection systemis disposed so that light rays are substantially perpendicularlyincident on the corneal surface and a diaphragm having substantially thesame size as the exit pupil diameter of the specular reflection light isdisposed in the vicinity of the exit pupil, thereby effectivelyacquiring the specular reflection light from the anterior eye segment ofthe subject's eye.

Japanese Unexamined Patent Application Publication No. 2001-309889discloses an ophthalmologic apparatus that performs color photography ofan interference pattern formed by the tear film to acquire time-seriesimages and obtains a time-dependent change in the hue of theinterference pattern from the time-series images, thereby carrying outan examination of the state of the tear film in an objective manner.

Japanese Unexamined Patent Application Publication No. 2005-211173discloses an ophthalmologic apparatus that performs color photography ofan interference pattern formed by the tear film to acquire an image andanalyzes the interference pattern for each color component of the imageto evaluate the degree of progress of dry eye syndrome, therebyquantifying the degree of progress of dry eye syndrome with highprecision and high accuracy.

Japanese Unexamined Patent Application Publication No. 2017-136212discloses an ophthalmologic apparatus that processes a plurality offront images obtained by successive photography of the anterior eyesegment of the subject's eye to evaluate the location and shape of a dryspot and the movement direction of tears around the dry spot, therebyevaluating the type of dry eye syndrome in an objective manner.

As disclosed in Japanese Unexamined Patent Application Publication No.2017-136212, one of the important items in dry eye syndrome evaluationis the locations of dry spots (more generally, the distribution of thethicknesses of tears or the distribution of the state abnormalities oftears). As a matter of course, it is unknown in which part of theanterior eye segment an abnormality will have occurred before theexamination. Therefore, it is desirable for an examiner to be able toobserve a wide area of the anterior eye segment in order not to overlookthe abnormalities occurring in the periphery or edge of the cornea aswell as in order to improve the efficiency of the examination.

Further, in the case of presenting examination results, it is desirableto display the locations or distribution of abnormalities over theanterior eye segment image so that the examiner can easily (intuitively)find the abnormal areas in the anterior eye segment. This anterior eyesegment image is desired to be an image of a wide area in the anterioreye segment.

Furthermore, taking into consideration the possibility of occurrence ofmisregistration between the interference pattern image and the anterioreye segment image due to eye movements or body movements, is desirableto perform photographing of the interference pattern for obtaining thelocations or distribution of abnormalities and photographing of theanterior eye segment for obtaining an anterior eye segment image, atalmost the same time.

SUMMARY

The following presents a simplified summary of the innovation in orderto provide a basic understanding of some aspects described herein. Thissummary is not an extensive overview of the claimed subject matter. Itis intended to neither identify key or critical elements of the claimedsubject matter nor delineate the scope of the subject innovation. Itssole purpose is to present some concepts of the claimed subject matterin a simplified form as a prelude to the more detailed description thatis presented later.

An ophthalmologic apparatus according to some aspects includes anillumination system, an interference photographing system, an anterioreye segment photographing system, a first optical path coupling element,and a controller. The illumination system is configured to projectillumination light output from a light source, onto the anterior eyesegment of a subject's eye. The interference photographing system isconfigured for photographing an interference pattern formed on thecornea by the illumination light. The anterior eye segment photographingsystem is configured for photographing the anterior eye segment ontowhich the illumination light is being projected. The first optical pathcoupling element couples the optical path of the interferencephotographing system and the optical path of the anterior eye segmentphotographing system with one another. The controller is configured tocontrol a display device to display an interference image acquired bythe interference photographing system, over an anterior eye segmentimage acquired by the anterior eye segment photographing system.

According to some aspects, it is possible to present the parts whereabnormalities of the state of tears have occurred over a wide area inthe anterior eye segment with good locational precision.

The following description and the annexed drawings set forth in detailcertain illustrative aspects of the claimed subject matter. Theseaspects are indicative, however, of but a few of the various ways inwhich the principles of the innovation may be employed and the claimedsubject matter is intended to include all such aspects and theirequivalents. Other advantages and novel features of the claimed subjectmatter will become apparent from the following detailed description ofthe innovation in view of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of theconfiguration of an ophthalmologic apparatus according to an exemplaryembodiment.

FIG. 2 is a schematic diagram illustrating an example of theconfiguration of the ophthalmologic apparatus according to the exemplaryembodiment.

FIG. 3 is a schematic diagram for describing an example of theconfiguration of the ophthalmologic apparatus according to the exemplaryembodiment.

FIG. 4 is a flowchart illustrating an example of the operation of theophthalmologic apparatus according to the exemplary embodiment.

FIG. 5A is a schematic diagram illustrating an example of theconfiguration of an ophthalmologic apparatus according to a modificationexample.

FIG. 5B is a schematic diagram illustrating an example of theconfiguration of the ophthalmologic apparatus according to themodification example.

FIG. 6 is a schematic diagram illustrating an example of theconfiguration of the ophthalmologic apparatus according to themodification example.

DETAILED DESCRIPTION

A purpose of some exemplary embodiments is to make it possible topresent the parts where abnormalities of the state of tears haveoccurred over a wide area in the anterior eye segment with goodlocational precision.

An ophthalmologic apparatus according to the first aspect of someexemplary embodiments includes an illumination system, an interferencephotographing system, an anterior eye segment photographing system, afirst optical path coupling element, and a controller. The illuminationsystem is configured to project illumination light output from a lightsource, onto the anterior eye segment of a subject's eye. Theinterference photographing system is configured for photographing aninterference pattern formed on the cornea by the illumination light. Theanterior eye segment photographing system is configured forphotographing the anterior eye segment onto which the illumination lightis being projected. The first optical path coupling element couples theoptical path of the interference photographing system and the opticalpath of the anterior eye segment photographing system with one another.The controller is configured to control a display device to display aninterference image acquired by the interference photographing system,over an anterior eye segment image acquired by the anterior eye segmentphotographing system.

The second aspect of some exemplary embodiments is the ophthalmologicapparatus of the first aspect and further includes a first lens groupdisposed in a position between the subject's eye and the first opticalpath coupling element and a second lens group disposed in a position onan opposite side of the subject's eye with respect to the first opticalpath coupling element. The combination of the first lens group and thesecond lens group functions as an objective lens of the interferencephotographing system. In addition, the first lens group functions as anobjective lens of the anterior eye segment photographing system.

The third aspect of some exemplary embodiments is the ophthalmologicapparatus of the second aspect in which a lens located closest to thefirst optical path coupling element among lenses included in theanterior eye segment photographing system is disposed at the focalposition of the first lens group or in a vicinity thereof.

The fourth aspect of some exemplary embodiments is the ophthalmologicapparatus of any of the first to third aspects and further includes asecond optical path coupling element that couples the optical path ofthe illumination system and the optical path of the interferencephotographing system with one another.

The fifth aspect of some exemplary embodiments is the ophthalmologicapparatus of the fourth aspect in which each of the first optical pathcoupling element and the second optical path coupling element is a beamsplitter. In addition, returning light of the illumination light forphotographing the interference pattern, is reflected by each of thefirst optical path coupling element and the second optical path couplingelement and guided to an image sensor provided in the interferencephotographing system.

The sixth aspect of some exemplary embodiments is the ophthalmologicapparatus of any of the first to fifth aspects and further includes anillumination intensity changing device that changes the intensity of theillumination light projected onto the anterior eye segment.

The seventh aspect of some exemplary embodiments is the ophthalmologicapparatus of any of the first to sixth aspects and further includes anexcitation filter and a barrier filter. The excitation filter isconfigured to generate excitation light for a fluorescent agentadministered to the anterior eye segment, from the illumination light.The barrier filter is configured to selectively pass fluorescenceemitted from the fluorescent agent that has absorbed the excitationlight.

The eighth aspect of some exemplary embodiments is the ophthalmologicapparatus of any of the first to seventh aspects and further includes aprojection system, a detection system, and a first alignment device. Theprojection system is configured to project alignment light onto theanterior eye segment along a direction non-parallel to the optical axisof the optical path from the first optical path coupling element towardthe subject's eye. The detection system is configured to detectreflected light of the alignment light from the anterior eye segment.The first alignment device is configured to perform alignment in thedirection along the optical axis, based on an output from the detectionsystem.

The ninth aspect of some exemplary embodiments is the ophthalmologicapparatus of the eighth aspect in which the projection system includesan alignment light source that outputs the alignment light and thedetection system includes an image sensor that detects the reflectedlight. In addition, each of the alignment light source and the imagesensor is disposed in a position on the opposite side of the subject'seye with respect to the first optical path coupling element.

The tenth aspect of some exemplary embodiments is the ophthalmologicapparatus of any of the first to ninth aspects and further includes asecond alignment device. The second alignment device is configured toperform alignment in a direction perpendicular to the optical axis ofthe optical path from the first optical path coupling element toward thesubject's eye, based on an anterior eye segment image acquired by theanterior eye segment photographing system.

The eleventh aspect of some exemplary embodiments is the ophthalmologicapparatus of any of the first to seventh aspects and further includestwo or more photographing devices and a third alignment device. The twoor more photographing devices are configured to photograph the anterioreye segment from directions different from each other. The thirdalignment device is configured to perform three dimensional alignmentbased on two or more photographed images respectively acquired by thetwo or more photographing devices.

An ophthalmologic apparatus according to some exemplary embodiments willbe described in detail below with referring to the drawings.

First, the outline of the embodiment will be described. Theophthalmologic apparatus of the embodiment is configured to acquire aninterference image by photographing an interference pattern representingthe state of the tears on the cornea, acquire an anterior eye segmentimage by photographing the anterior eye segment, and overlay theinterference image on the anterior eye segment image. At least part ofthe element group for interference photographing (i.e., at least part ofthe interference photographing system) is different from the elementgroup for anterior eye segment photographing (i.e., the anterior eyesegment photographing system).

The presented interference image may be an interference image itself (araw image) acquired by the interference photographing system, or aninterference image (a processed image) obtained by processing the rawimage. The processed image may be, for example, a color map thatrepresents a parameter distribution obtained from a raw image in pseudocolors, or a map that represents a region where parameter values belongto a predetermined range. This parameter may be, for example, thethickness of any one of the lipid layer, the aqueous layer and themucinous layer of the tear film, the thickness of any two layers, or thethickness of the three layers. Further, the processed image may becreated by applying any kind of image processing such as correction,adjustment or enhancement, to the raw image.

Likewise, the presented anterior eye segment image may be an anterioreye segment image itself (a raw image) acquired by the anterior eyesegment photographing system, or an anterior eye segment image (aprocessed image) obtained by processing the raw image. The processedimage may be created by applying any kind of image processing such ascorrection, adjustment or enhancement, to the raw image, for example.

The display device on which the interference image and the anterior eyesegment image are displayed may be a part of the ophthalmologicapparatus according to the embodiment, or may not. In the latter case,the display device is a peripheral device of the ophthalmologicapparatus according to the embodiment.

In the present specification, unless otherwise mentioned, “image data”and an “image” based on the image data are not distinguished from eachother. Likewise, a site or a tissue of the subject's eye and an imagerepresenting the site or the tissue are not distinguished from eachother, unless otherwise mentioned.

Further, in the present specification, unless otherwise mentioned, a“lens” refers to a single lens or a combination of two or more lenses.Likewise, unless otherwise mentioned, a “lens group” refers to acollection of two or more lenses or a single lens.

In addition, In the present specification, the term “processor” is usedto mean, for example, a circuitry or a circuit such as a centralprocessing unit (CPU), a graphics processing unit (GPU), an applicationspecific integrated circuit (ASIC), a programmable logic device (forexample, a simple programmable logic device (SPLD), a complexprogrammable logic device (CPLD), or a field programmable gate array(FPGA)), or other circuitry or circuit. The processor realizes thefunctions according to the embodiment, for example, by reading out andexecuting a program stored in a storage circuit or a storage device.

<Configuration>

FIG. 1 and FIG. 2 show an example of the configuration of theophthalmologic apparatus according to the embodiment. The ophthalmologicapparatus 1 has following functions: a function of photographing aninterference pattern representing the state of tears on the cornea Ec ofthe subject's eye E; a function of photographing the anterior eyesegment Ea; and a function of presenting an interference imagerepresenting the interference pattern over an anterior eye segmentimage.

As an exemplary configuration for realizing these functions, theophthalmologic apparatus 1 includes the examination unit 2, the unitmovement mechanism 70, the display device 80, the operation device 90,and the computer 100. The computer 100 may be, for example, an embeddedsystem of the ophthalmologic apparatus 1.

The examination unit 2 stores various kinds of optical systems andvarious kinds of mechanisms. The exemplary examination unit 2 includesthe illumination system 10, the interference photographing system 20,the anterior eye segment photographing system 30, the first lens groupincluding the two lenses 41 and 42, the second lens group including thetwo lenses 43 and 44, the optical path coupling element 51, thereflection mirror 52, the optical path coupling element 53, thealignment light source 61, and the image sensor 62.

The illumination system 10 is configured to project illumination lightonto the anterior eye segment Ea of the subject's eye E. The exemplaryillumination system 10 includes the illumination light source 11, thecollimator lens 12, the excitation filter 13, and the variable filter14. The optical path of the illumination system 10 is formed by theillumination light source 11, the collimator lens 12, the excitationfilter 13, the variable filter 14, (the optical path coupling element53,) the reflection mirror 52, the lens 44, the lens 43, the opticalpath coupling element 51, the lens 42, and the lens 41.

The illumination light source 11 emits the illumination light. Theoperation of the illumination light source 11 is controlled by thecomputer 100.

The collimator lens 12 converts the illumination light output from theillumination light source 11 into a parallel light beam. The collimatorlens 12 consists of, for example, a single lens or a combination of twoor more lenses.

The excitation filter 13 is placed in the optical path (as shown by thesolid line) when the modality of the anterior eye segment photographingis set to fluorescent contrast photographing, and is placed outside theoptical path (as shown by the dotted line) in other cases. The movementof the excitation filter 13 is performed by the excitation filtermovement mechanism 13A. The excitation filter movement mechanism 13Aincludes an actuator that operates in accordance with a command issuedfrom the computer 100. The actuator may be, for example, a solenoidactuator.

In fluorescent contrast photographing, a fluorescent agent (afluorescent dye) is administered to the anterior eye segment Ea. Theexcitation filter 13 generates excitation light for the fluorescentagent from the illumination light. More specifically, the excitationfilter 13 selectively passes the wavelength that excites the fluorescentagent. In a typical example, the fluorescent dye is fluorescein and thetransmitting center wavelength of the excitation filter 13 is set at theabsorption maximum wavelength of fluorescein of 494 nm, or near theabsorption maximum wavelength (e.g., at a wavelength within the rangefrom 490 nm to 500 nm).

The variable filter 14 is an optical element for changing the intensity(light amount) of the illumination light projected onto the subject'seye E. Since it takes a certain amount of time (e.g., 10 seconds ormore) to evaluate the time-dependent change of the interference patterncaused by tears, it is considered desirable to be capable of regulatingthe intensity of the illumination light so that the subject is able tohave his/her eyes open during the entire period of time. The variablefilter 14 is an example of elements to realize such a request.

The variable filter 14 may include, for example, one or both of aneutral density filter (ND filter) and a band pass filter (BPF). Thevariable filter 14 includes a single filter or two or more filters.

When the variable filter 14 consists of a single filter, the variablefilter 14 is, for example, an optical filter whose filter characteristic(e.g., transmission characteristic, absorption characteristic) can varyin a continuous or discrete manner. The computer 100 performs controlfor hanging the filter characteristic.

When the variable filter 14 includes two or more filters, these filtersare selectively placed in the optical path. As a typical example of thiscase, the variable filter 14 includes two or more filters mounted in aturret and an actuator that moves (typically rotates) the turret. Theactuator may be, for example, a pulse motor operated by a command (pulsecontrol signal) issued from the computer 100.

Note that the intensity of the illumination light projected onto thesubject's eye E can be changed without using the variable filter 14. Forexample, some exemplary embodiments may be configured to vary one orboth of the intensity and the wavelength band of the illumination lightoutput by the illumination light source (11), to change the intensity ofthe illumination light projected onto the subject's eye E. Further, someexemplary embodiments may be configured to change the intensity of theillumination light projected onto the subject's eye E, by means of acombination of the illumination light source control and the variablefilter control.

Further, one or more of the two or more filters provided in the variablefilter 14 may be the excitation filter 13. In the case where theexcitation filter 13 is included in the variable filter 14, the computer100 controls the variable filter 14 to perform insertion and removal ofthe excitation filter 13 into and from the optical path when thefluorescent contrast photographing is carried out.

According to the illumination system 10 of the present example, theillumination light output from the illumination light source 11 isconverted into a parallel light beam by the collimator lens 12. Whenapplying the fluorescent contrast photographing, the illumination lightthat has passed through the collimator lens 12 becomes excitation lightby the excitation filter 13, and the intensity of the excitation lightis regulated by the variable filter 14. When applying a modality otherthan the fluorescent contrast photographing, the intensity of theillumination light that has passed through the collimator lens 12 isregulated by the variable filter 14. The illumination light (theexcitation light) that has passed through the variable filter 14 furtherpasses through the optical path coupling element 53, the reflectionmirror 52, the lens 44, the lens 43, the optical path coupling element51, the lens 42, and the lens 41, and then is projected onto theanterior eye segment Ea.

The interference photographing system 20 is configured to photograph aninterference pattern formed on the cornea by the illumination lightprojected onto the anterior eye segment Ea by the illumination system10. The interference pattern is formed by the illumination light beingreflected at layers (layer boundaries) of the tear film. For example,the reflected light from the front surface of the lipid layer of thetear film and the reflected light from the back surface interfere witheach other, whereby a pattern corresponding to the distribution of thethicknesses of the lipid layer is formed.

The interference photographing system 20 includes the diaphragm 21, thetelecentric lens 22, and the interference photographing camera 23. Theoptical path of the interference optical system 20 is formed by the lens41, the lens 42, the optical path coupling element 51, the lens 43, thelens 44, the reflection mirror 52, the optical path coupling element 53,the diaphragm 21, the telecentric lens 22, and the interferencephotographing camera 23.

The diaphragm 21 is an optical element for limiting (regulating) theamount of light guided to the interference photographing camera 23. Thediaphragm 21 may be a variable diaphragm controlled by the computer 100.

The telecentric lens 22 may be, for example, an image-space telecentriclens. By employing an image-space telecentric lens, light rays areincident on the entire photo-detection surface of the interferencephotographing camera 23 in a substantially perpendicular manner. Thiscan lead to the elimination of roll-off and vignetting, and further leadto the equalization of the peripheral light amount ratio. Thetelecentric lens 22 consists of, for example, a single lens or acombination of two or more lenses.

The interference photographing camera 23 detects the light that haspassed through the telecentric lens 22 and generates an image (aninterference image) representing the interference pattern formed on thecornea. The interference photographing camera 23 has sensitivity atleast in the visible spectrum. The interference photographing camera 23may be, for example, a color video camera, typically a three-CCD videocamera, or a three-CMOS video camera. Such a configuration enables toobtain various color components of the interference image.

The reflected light of the illumination light projected onto theanterior eye segment Ea by the illumination system 10, passes throughthe lens 41, the lens 42, the optical path coupling element 51, the lens43, the lens 44, the reflection mirror 52, the optical path couplingelement 53, the diaphragm 21 and the telecentric lens 22, and then isincident onto the interference photographing camera 23.

The anterior eye segment photographing system 30 is configured tophotograph the anterior eye segment Ea onto which the illumination lightis projected by the illumination system 10. The anterior eye segmentphotographing system 30 includes the barrier filter 31, the lens 32, andthe anterior eye segment photographing camera 33. The optical path ofthe anterior eye segment photographing system 30 is formed by the lens41, the lens 42, (the optical path coupling element 51,) the barrierfilter 31, the lens 32, and the anterior eye segment photographingcamera 33.

The barrier filter 31 is placed in the optical path (in the state shownby the solid line) when the modality of the anterior eye segmentphotographing is set to the fluorescent contrast photographing, and isplaced outside the optical path (in the state shown by the dotted line)in other cases. The movement of the barrier filter 31 is performed bythe barrier filter movement mechanism 31A. The barrier filter movementmechanism 31A includes an actuator that operates in accordance with acommand issued from the computer 100. The actuator may be, for example,a solenoid actuator.

The computer 100 executes synchronous control of the operation of theexcitation filter movement mechanism 13A and the operation of thebarrier filter movement mechanism 31A. More specifically, when themodality of the anterior eye segment photographing is set to thefluorescent contrast photographing, the computer 100 controls theexcitation filter movement mechanism 13A and the barrier filter movementmechanism 31A so that both the excitation filter 13 and the barrierfilter 31 are placed in the respective optical paths. In addition, whenthe modality of the anterior eye segment photographing is set to amodality other than the fluorescent contrast photographing, the computer100 controls the excitation filter movement mechanism 13A and thebarrier filter movement mechanism 31A so that both the excitation filter13 and the barrier filter 31 are placed outside the respective opticalpaths.

In the fluorescent contrast photographing, the fluorescent agent (thefluorescent dye) administered to the anterior eye segment Ea absorbs theexcitation light generated by the excitation filter 13 and emitsfluorescence of a specific wavelength. The barrier filter 31 selectivelypasses the wavelength of the fluorescence. As a typical example, whenthe fluorescent dye is fluorescein, the transmitting center wavelengthof the barrier filter 13 is set at the emission maximum wavelength offluorescein of 521 nm, or near the emission maximum wavelength.

The lens 32 is, for example, an imaging lens that forms an image on thephoto-detection surface of the anterior eye segment photographing camera33. Alternatively, as with the interference photographing system 20, thelens 32 may be a telecentric lens (an image-space telecentric lens). Thelens 32 consists of, for example, a single lens or a combination of twoor more lenses.

A lens located closest to the optical path coupling element 51 among thelenses 32 is disposed at the focal position of the first lens groupconsisting of the two lenses 41 and 42, or in the vicinity of the focalposition. When the lens 32 consists of a single lens, the lens 32 isdisposed at or near the back focal position of the first lens group.When the lens 32 consists of two or more lenses, the lens closest to theoptical path coupling element 51 among the two or more lenses, that is,the lens located closest to the subject's eye E, is disposed at or nearthe back focal position of the first lens group. With such anarrangement, the field of view of the anterior eye segment photographingcamera 33 can be widened to capture a wide area of the anterior eyesegment Ea.

The anterior eye segment photographing camera 33 photographs theanterior eye segment Ea by detecting the light that has passed throughthe lens 32. This acquires an anterior eye segment image. The anterioreye segment photographing camera 33 has sensitivity at feast in thewavelength range for the fluorescent contrast photographing. Forexample, the anterior eye segment photographing camera 33 hassensitivity in the visible spectrum and the infrared spectrum. Theanterior eye segment photographing camera 33 may be, for example, acolor video camera or a monochrome video camera, and may typically be aCCD video camera, a three-CCD video camera, a CMOS video camera, or athree-CMOS video camera.

The first lens group consisting of the two lenses 41 and 42 is disposedin a position between the subject's eye E and the optical path couplingelement 51. The second lens group consisting of the two lenses 43 and 44is disposed in a position on the opposite side of the subject's eye Ewith respect to the optical path coupling element 51. In other words,the second lens group is disposed in a position between the interferencephotographing camera 23 and the optical path coupling element 51.

For example, the surface of the lens 41 on the side of the subjects eyeE (the front surface) is formed in a concave shape or a planar shape,and the surface opposite to the subject's eye E (the back surface) isformed in a convex aspherical shape. As for the lens 42, for example,both the front surface and the back surface are formed in a convex shapeor a planar shape.

The lens 43 and the lens 44 form a cemented lens (doublet). The lens 43is formed in a convex shape on both the front surface and the backsurface, for example. As for the lens 44, for example, both the frontsurface and the back surface formed in a concave shape.

Such a lens configuration is designed to satisfy the following twoconditions: (1) the illumination light is incident substantiallyperpendicular to each position on the cornea Ec; (2) the reflected lightfrom each position on the cornea Ec travels, up to the lens 41, throughthe route substantially the same as the path of the illumination lightincident on the concerned position in the opposite direction, and thenis detected by the interference photographing system 20.

It can be seen from the light ray diagram (diagram of a simulationresult) of FIG. 3, that the interference photographing system 20according to the present example satisfies the above two conditions.Incidentally, although there is some description relating to the twoconditions in Japanese Unexamined Patent Application Publication No.1997-289970, no specific and concrete optical system that actuallysatisfies the two conditions has been disclosed in known literatures,and it is thought that the present inventors have devised such anoptical system for the first time.

By applying the optical system that satisfies the above two conditions,the path of the illumination light corresponding to each position on thecornea Ec and the path of the reflected light thereof substantiallycoincide with each other. As a result of this, the distribution of thestate of tears on the curved surface of the cornea Ec, can be graspedaccurately from the directions each perpendicular to the curved surface.

Configurations for satisfying the aforementioned two conditions are notlimited to the above. As a result of earnest research, the inventorshave found out that at least each of the following optical systemconfigurations (A) to (C) satisfies the above two conditions. Note thatthese are merely examples, and any modification (omission, substitution,addition, etc.) is permissible.

(A) In an optical system configuration of the present example, thefollowing three lenses may be used in place of the four lenses 41 to 44shown in FIG. 1. The first lens closest to the subject's eye has thefront surface formed in a concave shape and the back surface formed in aconvex aspherical shape. The second lens adjacent to the first lens isformed in a convex shape on both the front surface and the back surface.The third lens, the front surface of which is affixed to the backsurface of the second lens, has the front surface formed in a concaveshape and the back surface formed in a convex shape.

(B) In an optical system configuration of the present example, thefollowing four lenses may be used in place of the four lenses 41 to 44shown in FIG. 1. The first lens closest to the subject's eye has thefront surface formed in a gentle convex shape or a planar shape, and theback surface formed in a convex aspherical shape. The second lenssecond-closest to the subject's eye after the first lens is formed in aconvex shape on both the front surface and the back surface. The thirdlens, the front surface of which is affixed to the back surface of thesecond lens, has the front surface formed in a concave shape and theback surface formed in a convex shape. The fourth lens, the frontsurface of which faces the back surface of the third lens, has the frontsurface formed in a convex shape and the back surface formed in aconcave shape.

(C) In an optical system configuration of the present example, thefollowing five lenses may be used in place of the four lenses 41 to 44shown in FIG. 1. The first lens closest to the subject's eye has thefront surface formed in a planar shape or a concave shape, and the backsurface formed in a convex aspherical shape. The second lens adjacent tothe first lens has the front surface formed in a planar shape and theback surface formed in a convex shape. The third lens adjacent to thesecond lens is formed in a convex shape on both the front surface andthe back surface. The fourth lens, the front surface of which is affixedto the back surface of the third lens, has the front surface formed in aconcave shape and the back surface formed in a convex shape. The fifthlens adjacent to the fourth lens has the front surface formed in aconvex shape and the back surface in a concave shape.

In the example shown in FIG. 1, the four lenses 41, 42, 43 and 44, thatis, the first lens group and the second lens group, function as anobjective lens of the interference photographing system 20. Further, thetwo lenses 41 and 42, that is, the first lens group, function as anobjective lens of the anterior eye segment photographing system 30.

According to such a configuration, as to the interference photographingsystem 20, the illumination light can be made incident substantiallyperpendicularly to each position on the cornea Ec, and the reflectedlight from each position on the cornea Ec can be directed to travelalong substantially the same route as the incident path. In addition, asto the anterior eye segment photographing system 30, a wide field ofview can be secured, that is, a wide area of the anterior eye segment Eacan be imaged.

The light detected by the interference photographing system 20 and thelight detected by the anterior eye segment photographing system 30 areboth returning lights from the anterior eye segment Ea, but differentfrom each other. Those skilled in the art will appreciate that it is noteasy to configure an optical system capable of detecting such differentlights separately by means of individual optical systems configured tosatisfy requirements different from each other.

The optical path coupling element 51 is an optical element that couplesthe optical path of the interference photographing system 20 and theoptical path of the anterior eye segment photographing system 30. Forexample, the optical path coupling element 51 couples the optical pathof the interference photographing system 20 and the optical path of theanterior eye segment photographing system 30 in a coaxial manner (Inother words, the optical path coupling element 51 couples the opticalpaths in the way that their optical axes intersect each other).

The optical path coupling element 51 may be any type of beam splitter.In the present example, a half mirror can be used as the optical pathcoupling element 51 since the interference photographing system 20 usesbroadband visible light and the anterior eye segment photographingsystem 30 uses visible fluorescence (fluorescein). Further, in theexample shown in FIG. 1, the optical path coupling element 51 also has afunction of coupling the optical path of the illumination system 10 andthe optical path of the anterior eye segment photographing system 30.

In some exemplary embodiments, a dichroic mirror can be used as theoptical path coupling element 51 when adopting a configuration thatseparates the passing light (transmitted light) and the reflected lightin terms of wavelengths. In some other exemplary embodiments, apolarization beam splitter can be used as the optical path couplingelement 51 when adopting a configuration that separates the passinglight (transmitted light) and the reflected light in terms ofpolarization. Note that these are merely illustrative examples of anelement (first optical path coupling element) for coupling the opticalpath of the interference photographing system and the optical path ofthe anterior eye segment photographing system, and any modification(omission, substitution, addition, etc.) is allowable.

The reflection mirror 52 changes the direction of the optical path ofthe illumination system 10 and that of the optical path of theinterference photographing system 20. This makes it possible to make theconfiguration of the optical system compact, and as a result, it becomespossible to downsize the ophthalmologic apparatus 1. It should be notedthat any kind of elements and any kind of configurations can be employedfor this purpose or other purposes. For example, the position,arrangement angle, number, size, etc. of the reflection mirror may bedesigned in an appropriate manner. Further, an element different fromthe reflection mirror may be used.

The optical path coupling element 53 is an optical element that couplesthe optical path of the illumination system 10 and the optical path ofthe interference photographing system 20. For example, the optical pathcoupling element 53 couples the optical path of the illumination system10 and the optical path of the interference photographing system 20 in acoaxial manner.

The optical path coupling element 53 may be any type of beam splitter.In the present example, a half mirror can be used as the optical pathcoupling element 53 since the illumination system 10 and theinterference photographing system 20 both use broadband visible light.As with the optical path coupling element 51, a dichroic mirror, apolarizing beam splitter or another type of beam splitter can be adoptedinstead of a half mirror as needed.

In the example shown in FIG. 1, the light guided by the interferencephotographing system 20 (that is, the returning light of theillumination light for photographing the interference pattern caused bythe tears on the cornea Ec) is guided via the two beam splitters and isreflected by the both beam splitters. More specifically, the lightguided by the interference photographing system 20 is reflected by theoptical path coupling element 51 and also reflected by the optical pathcoupling element 53, and directed to the interference photographingcamera 23.

This configuration is intended to avoid disturbance of light as itpasses through a beam splitter. The present configuration makes itpossible to detect the interference pattern on the cornea Ec with highaccuracy.

The alignment light source 61 and the image sensor 62 are used foralignment in the direction along the optical axis of the lens 41(referred to as Z alignment in the Z direction). The alignment lightsource 61 projects light e.g., infrared light) for Z alignment onto thesubject's eye E. The light output from the alignment light source 61 isprojected in an oblique manner onto the cornea Ec via the lens 42 andthe lens 41. The reflected light of the projected light at the corneaforms an image on the photo-detection surface of the image sensor 62 bythe lens 41 and the lens 42 (as well as by other lenses not shown in thefigures).

The image sensor 62 may be any type of one or two dimensional imagesensor. In other words, the image sensor 62 provided in the Z alignmentsystem may be any type of image sensor in which a plurality of lightdetecting elements (e.g., photodiodes) are arranged in one or twodimensional manner. The image sensor 62 is typically a line sensor.

In some exemplary embodiments, the light emitted by the alignment lightsource 61 and traveling toward the lens 42 passes through a notch, anaperture, or a light transmitting part formed in the optical pathcoupling element 51, for example, and then reaches the lens 42.Similarly, the light traveling from the lens 42 toward the image sensor62 passes through a notch, an aperture, or a light transmitting partformed in the optical path coupling element 51, for example, and reachesimage sensor 62. Such a configuration makes it possible to provideelements for alignment while satisfying the above-described conditionsregarding the interference photographing system 20 and enlarging thefield of view of the anterior eye segment photographing system 30.

The change in the position of the cornea Ec (e.g., the corneal apex) inthe Z direction causes the change in the projection position of thelight on the photo-detection surface of the image sensor 62. Thecomputer 100 can determine the position of the cornea Ec (e.g., thecorneal apex) based on the position at which the image sensor 62 hasdetected the light. Further, the computer 100 performs the Z alignmentof the examination unit 2 by controlling the unit movement mechanism 70based on the determined position of the cornea Ec (e.g., the cornealapex). The present Z alignment method is an example ofoptical-lever-based alignment techniques.

The unit movement mechanism 70 moves the examination unit 2 in a threedimensional manner. In a typical example, the unit movement mechanism 70includes the followings: a Z stage that is movable in the Z direction(i.e., the front and back directions); a Z movement mechanism that movesthe Z stage; an X stage that is movable in the X direction (i.e., theleft and right directions or the horizontal direction) perpendicular tothe Z direction; an X movement mechanism that moves the X stage; a Ystage that is movable in the Y direction (i.e., the up and downdirections or the vertical direction) perpendicular to both the Zdirection and the X direction; and a Y movement mechanism that moves theY stage. Each of these movement mechanisms includes an actuator (e.g.; apulse motor) that operates under the control of the computer 100.

The display device 80 functions as a part of the user interface device;and displays information under the control of the computer 100. Thedisplay device 80 may be, for example, a liquid crystal display (LCD) oran organic light emitting diode (OLED) display.

The operation device 90 functions as a part of the user interface deviceand is used for manually operating the ophthalmologic apparatus 1. Theoperation device 90 may include any kinds of hardware keys, such as ajoystick, buttons, and switches, provided in the ophthalmologicapparatus 1. In addition, the operation device 90 may include any kindsof peripheral devices, such as a keyboard, a mouse, a joystick, and anoperation panel, connected to the ophthalmologic apparatus 1. Inaddition, the operation device 90 may include any kinds of softwarekeys, such as buttons, icons, and menus, displayed on the touch panel.

The computer 100 executes various kinds of calculations and variouskinds of controls for operating the ophthalmologic apparatus 1. Thecomputer 100 includes one or more processors and one or more storagedevices. Examples of the storage devices include a random access memory(RAM), a read only memory (ROM), a hard disk drive (HDD), and a solidstate drive (SSD). Various kinds of computer programs are stored in thestorage devices, and the calculations and controls according to thepresent example are realized through the operations of the processor(s)executed based on the computer programs.

FIG. 2 shows an example of the configuration of the computer 100. Thecomputer 100 includes the examination processor 110, the displayprocessor 120, the illumination intensity changing processor 130, andthe alignment processor 140.

The examination processor 110 executes the processing (e.g.,calculations and controls) relating to the examination performed by theophthalmologic apparatus 1. The examination processor 110 is realized bycooperation of hardware including a processor and examination processingsoftware.

The examination processor 110 controls, for example, each of theillumination light source 11, the excitation filter movement mechanism13A, the interference photographing camera 23, the barrier filtermovement mechanism 31A, and the anterior eye segment photographingcamera 33.

The controls of the illumination light source 11 include, for example,turning on and off, changing the output light amount, and changing theoutput wavelength range (wavelength band). The controls of theexcitation filter movement mechanism 13A include, for example, theinsertion of the excitation filter 13 into the optical path and theremoval of the excitation filter 13 from the optical path.

The controls of the interference photographing camera 23 include, forexample, the exposure adjustment, the gain adjustment, the detectionrate adjustment, and the selection of the detection wavelength range(e.g., the selection of an image sensor to be used). Note that when thediaphragm 21 is a variable diaphragm, the examination processor 110 cancontrol the diaphragm 21.

The controls of the barrier filter movement mechanism 31A include, forexample, the insertion of the barrier filter 31 into the optical pathand the removal of the barrier filter 31 from the optical path. Thecontrols of the anterior eye segment photographing camera 33 include,for example, the exposure adjustment, the gain adjustment, and thedetection rate adjustment.

Furthermore, the examination processor 110 can perform processing andcalculations relating to an interference image obtained by theinterference photographing camera 23. For example, the examinationprocessor 110 can construct a processed image from a raw image acquiredby the interference photographing system 20. The processed image may be,for example, a color map that represents a parameter distributionobtained from a raw image in pseudo colors r a map that represents aregion where parameter values belong to a predetermined range. Thisparameter may be, for example, the thickness of any one of the lipidlayer, the aqueous layer and the mucinous layer of the tear film, thethickness of any two layers, or the thickness of the three layers.Further, the processed image may be created by applying any kind ofimage processing such as correction, adjustment or enhancement, to theraw image.

In addition, the examination processor 110 may be configured to executethe processing disclosed in any of Japanese Unexamined PatentApplication Publication No, 1997-289970, Japanese Unexamined PatentApplication Publication No. 2001-309889, Japanese Unexamined PatentApplication Publication No. 2005-211173, and Japanese Unexamined PatentApplication Publication No. 2017-136212, or other known processing. Forexample, the examination processor 110 may be capable of executing anyone or more of the followings: specification of a time-dependent changein the hue of an interference image (i.e., the hue of an interferencepattern); evaluation of the degree of progress of dry eye syndrome onthe basis of an interference pattern of a color component; evaluation ofthe location of a dry spot; evaluation of the shape of a dry spot; andevaluation of the direction of the movement of tears around the dryspot.

The examination processor 110 is capable of executing processing andcalculations relating to an anterior eye segment image obtained by theanterior eye segment photographing camera 33. For example, theexamination processor 110 can construct a processed image from a rawimage acquired by the anterior eye segment photographing system 30. Asdescribed above, the processed image may be created by applying any kindof image processing such as correction, adjustment or enhancement, tothe raw image.

The display processor 120 executes processing for displaying informationon the display device 80. The display processor 120 is realized bycooperation of hardware including a processor and display processingsoftware.

For example, in order to display the second information over the firstinformation, the display processor 120 executes, for example, thecontrol of presenting the second layer on the first layer, the controlof displaying the first information on the first layer, and the controlof displaying the second information on the second layer. Alternatively,the display processor 120 may execute the processing of composing thefirst information and the second information (e.g., the processing ofembedding the second information into the first information), and theprocessing of displaying the composite information thereby obtained.

The illumination intensity changing processor 130 executes processingfor changing the intensity of the illumination light projected onto theanterior eye segment Ea by the illumination system 10. The illuminationintensity changing processor 130 is realized by cooperation of hardwareincluding a processor and illumination intensity changing processingsoftware.

In the case where the variable filter 14 is used for changing theillumination intensity, the illumination intensity changing processor130 executes, for example, the control for changing the filtercharacteristic of the variable filter 14, or the control for placing oneof two or more filters in the optical path.

When changing the intensity of the illumination light projected onto theanterior eye segment Ea by changing any one or both of the intensity andthe wavelength band of the illumination light output by the illuminationlight source (11), the illumination intensity changing processor 130executes the control of the Illumination light source (11).

The illumination intensity changing processor 130 executes the controlfor changing the illumination intensity according to a signal sent fromthe operation device 90, for example. In other words, the ophthalmologicapparatus 1 may be configured so that the illumination intensity can bemanually changed. Here, the operation device 90 is operated by theexaminer or the subject. It should be noted that the variable range ofthe illumination intensity can be set in advance to a range appropriateto at least one of the interference photographing and the anterior eyesegment photographing.

In the case of automatically changing the illumination intensity, forexample, the illumination intensity changing processor 130 may beconfigured to acquire information on the illumination intensity appliedto the subject (i.e., the subject's eye E) in the past examination frommedical information (e.g., an electronic medical record) associated withthe subject, and to reproduce the illumination intensity acquired.

As another example in the case of automatic change of the illuminationintensity, the illumination intensity changing processor 130 may beconfigured to cause the ophthalmologic apparatus 1 to output visualinformation or auditory information for inquiring of the subject thedegree of glare when the illumination light is projected onto theanterior eye segment Ea, and to control the illumination intensityaccording to the subject's response to the inquiry.

As yet another example in the case of automatically changing theillumination intensity, the illumination intensity changing processor130 may be configured to regulate the illumination intensity based on abiosignal of the subject when the illumination light is being projectedonto the anterior eye segment Ea. This biosignal may be, for example,any of miosis neural oscillations (or brainwaves), heart rate,perspiration, facial expression and other signals. For example, theophthalmologic apparatus 1 includes a device for detecting any of thebiosignals or is connected to the device. Miosis can be detected, forexample, using the anterior eye segment photographing camera 33 and theillumination intensity changing processor 130. Neural oscillations canbe detected by using an electroencephalograph (EEG), for example. Theheart rate can be detected, for example, by an electrocardiograph (ECG)or a pulse oximeter. Perspiration can be detected by a perspirationmeter, for example. The facial expression can be detected, for example,by a camera and the illumination intensity changing processor 130. Abiosignal different from the above examples can be detected using acorresponding device.

The alignment processor 140 executes processing relating to the positionadjustment (alignment) of the optical system with respect to thesubject's eye E. The alignment processor 140 is realized by cooperationof hardware including a processor and alignment processing software.

In addition to the Z alignment, the ophthalmologic apparatus 1 may becapable of performing alignment in the X direction and the Y direction(i.e., XY alignment). The alignment processor 140 executes processingrelating to the Z alignment and processing relating to the XY alignment.

First, the processing relating to the Z alignment will be described. Thealignment processor 140 can execute the controls of the alignment lightsource 61 and the controls of the image sensor 62. The controls of thealignment light source include turning on and off, adjusting the lightamount, and adjusting the diaphragm, and other controls. The controls ofthe image sensor 62 include the exposure adjustment, the gainadjustment, the detection rate adjustment, and other controls.

Furthermore, the alignment processor 140 captures a signal output fromthe image sensor 62, and specifies the projection position of the lighton the photo-detection surface of the image sensor 62 based on thesignal captured. The alignment processor 140 determines the position ofthe corneal apex of the subject's eye E based on the projection positionspecified, and controls the unit movement mechanism 70 on the basis ofthe determined position to move the examination unit 2 in the frontdirection and/or the back direction (Z alignment).

Next, the XY alignment will be described. The ophthalmologic apparatus 1may be configured to perform the XY alignment based on an anterior eyesegment image acquired by the anterior eye segment photographing system30.

For example, the alignment processor 140 analyzes the acquired anterioreye segment image to detect a feature point such as the pupil center orthe center of gravity of the pupil. Next, the alignment processor 140calculates the deviation of the feature point from a predeterminedposition of the frame (e.g., from the center of the frame) of theanterior eye segment image. Subsequently, the alignment processor 140controls the unit movement mechanism 70 to move the examination unit 2in the horizontal direction and/or the vertical direction so as tocancel the calculated deviation (the XY alignment). As a result, the XYalignment can be performed so that the feature point of the anterior eyesegment is represented at the predetermined position of the frame.

The computer 100 may include an element different from those shown inFIG. 2. For example, the computer 100 may include a communicationinterface. The communication interface has a function for communicatingwith an external device (not shown in the figures). The external devicemay be one or more of any type of ophthalmologic apparatus, a devicethat reads information from a recording medium (i.e., a reader device),and a device that writes information into a recording medium (i.e., awriter device), for example. Further, the external device may be one ormore of any type of information processing device such as a hospitalinformation system (HIS) server, a digital imaging and communication inmedicine (DICOM) server, a doctor's terminal, a mobile terminal, apersonal terminal, a cloud server, and other devices.

<Operation>

The operation of the ophthalmologic apparatus 1 according to the presentembodiment will be described. FIG. 4 shows an example of the operationof the ophthalmologic apparatus 1.

(S1: Start Illumination of Anterior Eye Segment)

First, the illumination light source 11 is turned on and theillumination light is projected onto the anterior eye segment Ea.

(S2: Regulate Illumination Intensity)

Next, the intensity of the illumination light projected onto theanterior eye segment Ea is regulated by controlling the variable filter14 or other control. The illumination intensity can be regulated, forexample, in the manner described above.

(S3: Alignment)

Alignment is then performed. In the present embodiment, for example, theZ alignment is performed after the XY alignment. The XY alignment andthe Z alignment can be performed, for example, in the manner describedabove.

(S4: Place Fluorescent Contrast Photographing Filter in Optical Path)

Next, the excitation filter 13 and the barrier filter 31 arerespectively placed in the corresponding optical paths.

(S5: Begin Interference Photographing and Anterior Eye SegmentPhotographing)

When the above preparation is completed, the interference photographingby the interference photographing system 20 and the anterior eye segmentphotographing by the anterior eye segment photographing system 30 arebegun.

The interference photographing is performed to photograph aninterference pattern representing the state of tears on the cornea Ecsuch as the thickness distribution of the tears. The interferencephotographing is performed over a preset period, for example.Alternatively, the interference photographing is performed until thestate of the tears on the cornea Ec reaches a predetermined state (e.g.,until the tear film breakup has progressed up to a sufficient degree).

For example, the anterior eye segment photographing is performed duringat least part of the execution period of the interference photographing.This makes it possible to obtain an anterior eye segment image whoseacquisition time is substantially the same as that of a certaininterference image obtained by the interference photographing. When theanterior eye segment photographing is performed throughout the entireexecution period of the interference photographing, as in the case wherethe interference photographing and the anterior eye segmentphotographing are performed in parallel, it is possible to obtainanterior eye segment images temporally corresponding to respectiveinterference images acquired by the interference photographing.

The timings of the interference photographing and those of the anterioreye segment photographing can synchronized with each other. For example,the interference photographing and the anterior eye segmentphotographing can be performed at the same repetition timings (e.g., thesame imaging rate, the same frame rate).

(S6: Capture Interference Image and Anterior Eye Segment Image)

For example, the display processor 120 captures an interference imageand an anterior eye segment image acquired almost simultaneously witheach other. Alternatively, the display processor 120 may capture aninterference image and an anterior eye segment image acquired atsubstantially different timings from each other.

(S7: Overlay Interference Image on Anterior Eye Segment Image)

The display processor 120 displays the interference image and theanterior eye segment image captured in step S6 on the display device 80.In the present example, the display processor 120 displays theinterference image over the anterior eye segment image.

When an interference image and an anterior eye segment image acquiredalmost simultaneously with each other are captured in step S6, theophthalmologic apparatus 1 can overlay the interference image on theanterior eye segment images without performing registration betweenthese images.

On the other hand, when an interference image and an anterior eyesegment image acquired at substantially different timings from eachother are captured in step S6, it is desirable for the ophthalmologicapparatus 1 to perform registration between these images. However, thecontents represented in the interference image and the contentsrepresented in the anterior eye segment image are different from eachother, and thus, it is difficult to carry out registration between theseimages through direct comparison of these images.

Therefore, apart from the anterior eye segment image to be displayed,another anterior eye segment image (referred to as a supplementaryanterior eye segment image) acquired almost simultaneously with theinterference image is used. The selection of the supplementary anterioreye segment image can be performed based on, for example, thesynchronization between the interference photographing and anterior eyesegment photographing described above. The display processor 120 canexecute registration between the anterior eye segment image to bedisplayed and the supplementary anterior eye segment image, to determinethe deviation of the supplementary anterior eye segment image withrespect to the anterior eye segment image to be displayed. Further, thedisplay processor 120 can perform registration between the interferenceimage and the anterior eye segment image to be displayed so that thedeviation determined is canceled. This terminates the present operationexample (end).

Modification Example

The above embodiment performs the Z alignment using the optical leverand the XY alignment using the anterior eye segment image. The followingdescribes an example of an alignment method applicable to someembodiments instead of the Z alignment and the XY alignment.

The present modification example performs three dimensional alignment(XYZ alignment) based on two or more photographed images obtained byphotographing the anterior eye segment Ea from directions different fromeach other. FIGS. 5A, 5B, and 6 show a configuration example forrealizing the XYZ alignment. FIGS. 5A and 5B show an example of theexterior of the ophthalmologic apparatus according to the presentmodification example. The configuration shown in FIG. 6 can be appliedinstead of the configuration shown in FIG. 2.

For example, the configurations of the ophthalmologic apparatusaccording to the present modification example may be the same as thoseof the ophthalmologic apparatus 1 of the above embodiment, except forthe following points: in that the two anterior eye segment cameras 300Aand 300B are provided; in that the alignment processor 140A is providedin place of the alignment processor 140; and in that the alignment lightsource 61 and the image sensor 62 are not included. However, theophthalmologic apparatus according to the present modification mayinclude the alignment light source 61 and the image sensor 62. In thefollowing description, the same reference symbols as those of theophthalmologic apparatus 1 are used unless otherwise mentioned.

The ophthalmologic apparatus according to the modification example has achin rest and a forehead rest for supporting the face of the subject.The same may apply to the ophthalmologic apparatus 1 of the aboveembodiment.

The base 310 stores a driving system and a processing system. Forexample, the base 310 stores the unit movement mechanism 70 and thecomputer 100 shown in FIG. 1.

The housing 320 provided on the base 310 stores an optical system and adriving system. For example, the housing 320 stores the examination unit2 shown in FIG. 1.

The lens container 330 is provided in such a way that it protrudes fromthe front surface of the housing 320, and accommodates at least the lens41.

The display device 80 shown in FIG. 1 may be provided on the housing320. Further, the operation device 90 may be provided on at least one ofthe base 310 and the housing 320.

The two anterior eye segment cameras 300A and 300B are provided on thefront surface of the housing 320. The two anterior eye segment cameras300A and 300B photograph the anterior eye segment Ea of the subject'seye E from two directions different from each other (i.e., from twopositions different from each other).

Each of the two anterior eye segment cameras 300A and 300B includes animage sensor such as a CCD image sensor or a CMOS image sensor. In thepresent modification example, the two anterior eye segment cameras 300Aand 300B are provided on the surface of the housing 320 that faces thesubject. As shown in FIG. 5A, the two anterior eye segment cameras 300Aand 300B are provided at positions outside the optical path that passesthrough the lens 41.

Although the present modification example includes the two anterior eyesegment cameras 300A and 300B, the number of anterior eye segmentcameras provided may be two or more. Note that, in consideration of theprocessing load of calculation for three dimensional alignment, it issufficient as long as the anterior eye segment can be photographed fromtwo directions different from each other (but not limited to this).Alternatively, a movable anterior eye segment camera may be provided.The movable anterior eye segment camera can perform the anterior eyesegment photographing from two or more positions different from oneanother, in turn.

Although the present modification example is provided with the twoanterior eye segment cameras 300A and 300B separately from the anterioreye segment photographing system 30, one of two or more anterior eyesegment cameras may be the anterior eye segment photographing system 30in some embodiments.

When two or more anterior eye segment cameras are provided, theophthalmologic apparatus can photograph an anterior eye segment from twoor more directions different from one another in a substantiallysimultaneous manner. “Substantially simultaneous” refers to, as well asthe case where photographing timings by two or more anterior eye segmentcameras are simultaneous, a case where a time lag exists between thephotographing timings, wherein the time lag is to the extent that eyemovement can be ignored, for example. By performing such substantiallysimultaneous photographing, the ophthalmologic apparatus can acquire twoor more anterior eye segment images when the subject's eye issubstantially at the same position and orientation.

The photographing with two or more anterior eye segment cameras may beeither moving image photographing or still image photographing. In thecase of the moving image photographing, the above substantiallysimultaneous anterior eye segment photographing can be realized by thecontrol of matching the respective photographing start timings or by thecontrol of the respective frame rates or respective photographingtimings of frames. On the other hand, in the case of the still imagephotographing, substantially simultaneous anterior eye segmentphotographing can be realized by the control of matching the respectivephotographing timings.

The two anterior eye segment images acquired substantiallysimultaneously by the two anterior eye segment cameras 300A and 300B aresent to the computer 100.

The alignment processor 140A analyzes the two photographed images (theanterior eye segment images) substantially simultaneously acquired bythe two anterior eye segment cameras 300A and 300B, to determine thethree dimensional position of the subject's eye E.

This analysis may include, for example, the specification of a featureposition and the calculation of the three dimensional position thereof,as disclosed in U.S. Patent Application Publication No. 2015/0085252 A1.Prior to these processes, the ophthalmologic apparatus may executeprocessing for correcting the distortion of the photographed imageobtained by each of the two anterior eye segment cameras 300A and 300B.

In the specification of the feature position, the alignment processor140A analyzes each of the two anterior eye segment images acquiredsubstantially simultaneously by the two anterior eye segment cameras300A and 300B, for example, to specify a position (referred to as afeature position) in each photographed image corresponding to apredetermined feature site of the anterior eye segment Ea. The featuresite is typically the pupil center (or the center of gravity of thepupil).

In order to specify the position of the center of the pupil, thealignment processor 140A first specifies an image region correspondingto the pupil of the subject's eye E (a pupil region), based on thedistribution of the pixel values (e.g., brightness values) of thephotographed image. Generally, the pupil is depicted with lowerbrightness than other sites. Therefore, the pupil region can bespecified by searching for a low brightness image region. In thisprocess, the pupil region may be specified in consideration of the shapeof the pupil. More specifically, the alignment processor 140A may beconfigured to specify the pupil region by searching for an image regionof substantially circular shape and low brightness.

Next, the alignment processor 140A specifies the center position of thepupil region specified. As described above, the pupil is substantiallycircular shape. Therefore, the alignment processor 140A can specify thecontour of the pupil region, specify the center position of the contour(or specify the center position of an approximate circle or anapproximate ellipse of the contour), and set the specified centerposition to the pupil center.

In the calculation of the three dimensional position, the alignmentprocessor 140A calculates the three dimensional position of the featuresite of the subject's eye E, based on the respective positions of thetwo anterior eye segment cameras 300A and 300B and the feature positionsin the two photographed images specified by the above processes. Thiscalculation is carried out using trigonometry, as described in U.S.Patent Application Publication No. 2015/0085252 A1.

Based on the three dimensional position of the subject's eye Ecalculated in this manner, the alignment processor 140A controls theunit movement mechanism 70 so that the optical axis of the opticalsystem matches the axis of the subject's eye E, and controls the unitmovement mechanism 70 so that the distance between the subject's eye Eand the optical system matches a predetermined working distance. Here,the former process corresponds to the XY alignment and the latterprocess corresponds to the Z alignment.

Actions and Effects

Some actions and effects of the ophthalmologic apparatus according tosome exemplary embodiments will be described below.

The ophthalmologic apparatus according to some exemplary embodimentsincludes an illumination system, an interference photographing system,an anterior eye segment photographing system, a first optical pathcoupling element, and a controller.

The illumination system is configured to project illumination lightoutput from a light source, onto an anterior eye segment of a subject'seye. In the above example aspect, the illumination system 10 correspondsto the illumination system. The illumination system 10 is configured toproject the illumination light output from the illumination light source11 onto the anterior eye segment Ea.

The interference photographing system is configured to photograph aninterference pattern formed on the cornea by the illumination light thatprojected onto the anterior eye segment by the illumination system. Inthe above example aspect, the interference photographing system 20corresponds to the interference photographing system. The interferencephotographing system 20 acquires an interference image by photographingthe interference pattern formed on the cornea Ec by the illuminationlight that is projected onto the anterior eye segment Ea by theillumination system 10.

The anterior eye segment photographing system is configured tophotograph the anterior eye segment onto which the illumination light isbeing projected by the illumination system. In the above example aspect,the anterior eye segment photographing system 30 corresponds to theanterior eye segment photographing system. The anterior eye segmentphotographing system 30 photographs the anterior eye segment Ea ontowhich the illumination light is projected by the illumination system 10.The anterior eye segment photographing system 30 is configured tophotograph a wide area of the anterior eye segment Ea from the front.

The first optical path coupling element configured to couple the opticalpath of the interference photographing system and the optical path ofthe anterior eye segment photographing system with one another. In theabove example aspect, the optical path coupling element 51 correspondsto the first optical path coupling element. The optical path couplingelement 51 is configured to couple the optical path of the interferencephotographing system 20 and the optical path of the anterior eye segmentphotographing system 30. Furthermore, the optical path coupling element51 is configured to couple the optical path of the illumination system10 and the optical path of the anterior eye segment photographing system30.

The controller is configured to control a display device to display aninterference image acquired by the interference photographing systemover an anterior eye segment image acquired by the anterior eye segmentphotographing system. The displayed interference image may be a rawimage acquired by the interference photographing system or a processedimage obtained from the raw image. The display device may be an elementof the ophthalmologic apparatus or a peripheral device of theophthalmologic apparatus.

In the above example aspect, the computer 100 (particularly the displayprocessor 120) corresponds to the controller. The computer 100 isconfigured to display the interference image acquired by theinterference photographing system 20 over the anterior eye segment imageacquired by the anterior eye segment photographing system 30, on thedisplay device 80.

According to the exemplary embodiments thus configured, the interferencephotographing system and the anterior eye segment photographing systemare separately provided, and their optical paths are coupled with oneanother by the first optical path coupling element. Therefore, theophthalmologic apparatus can perform the interference photographing andthe anterior eye segment photographing almost at the same time. Thismakes it possible to reduce the possibility of occurrence of positionaldeviation (misregistration) between the interference image and theanterior eye segment image caused by eye movements and body movements.

Furthermore, according to the exemplary embodiments, the ophthalmologicapparatus can photograph a wide area of the anterior eye segments by theanterior eye segment photographing system provided separately from theinterference photographing system. This makes it possible to reduce thepossibility of overlooking an abnormality occurring in the periphery oredge of the cornea, and to perform the examination in an efficientmanner.

In addition, according to the exemplary embodiments, the ophthalmologicapparatus can overlay the interference image representing the state oftears on the anterior eye segment image. Therefore, the locations of theabnormalities of tears or the distribution of the abnormalities can beoverlaid on the anterior eye segment image. As a result, theophthalmologic apparatus can present the abnormality occurrencelocations to the user in a manner which the user can easily(intuitively) grasp the abnormality occurrence locations.

As described above, according to the exemplary embodiments, theophthalmologic apparatus can present the abnormality occurrencelocations of the state of tears over a wide area of the anterior eyesegment with good locational precision.

The ophthalmologic apparatus according to some exemplary embodiments mayfurther include a first lens group disposed in a position between thesubject's eye and the first optical path coupling element and a secondlens group disposed in a position on an opposite side of the subject'seye with respect to the first optical path coupling element. Here, acombination of the first lens group and the second lens group may beconfigured to function as an objective lens of the interferencephotographing system, and the first lens group may be configured tofunction as an objective lens of the anterior eye segment photographingsystem.

In the above example aspect, the two lenses 41 and 42 correspond to thefirst lens group, and the two lenses 43 and 44 correspond to the secondlens group. Furthermore, the four lenses 41 to 44 function as theobjective lens of the interference photographing system 22, and the twolenses 41 and 42 function as the objective lens of the anterior eyesegment photographing system 30.

In some exemplary embodiments, a lens located closest to the firstoptical path coupling element among lenses included in the anterior eyesegment photographing system, may be located at or near the focalposition of the first lens group.

In the above example aspect, the lens located closest to the opticalpath coupling element 51 among the lenses 32 included in the anterioreye segment photographing system 30, is located at or near the focalposition of the first lens group consisting of the two lenses 41 and 42.

According to the exemplary embodiments thus configured, at least thefollowing two effects are achieved. Firstly, regarding the interferencephotographing system, the ophthalmologic apparatus can make theillumination light incident substantially perpendicularly to eachposition on the cornea. In addition, the ophthalmologic apparatus candetect the reflected light from each position on the cornea thattravels, in the opposite direction, along substantially the same routeas the incident path of the illumination light to the each correspondingposition. This makes the path of the illumination light corresponding toeach position on the cornea and the path of the reflected light thereofsubstantially matched. As a result, the ophthalmologic apparatus candetect the distribution of the state of tears on the curved surface ofthe cornea, from the directions perpendicular to the curved surface.

Secondly, regarding the anterior eye segment photographing system, theanterior eye segment photographing system can be disposed near the firstoptical path coupling element, and further the anterior eye segmentphotographing system (lens therein) can be disposed at or near the backfocal position of the first lens group. This makes it possible to widenthe field of view of the anterior eye segment photographing system.

The ophthalmologic apparatus according to some exemplary embodiments mayfurther include a second optical path coupling element that couples theoptical path of the illumination system and the optical path of theinterference photographing system with one another. In the above exampleaspect, the optical path coupling element 53 corresponds to the secondoptical path coupling element. The optical path coupling element 53 isconfigured to couple the optical path of the illumination system 10 andthe optical path of the interference photographing system 20.

In some exemplary embodiments, each of the first optical path couplingelement and the second optical path coupling element may be a beamsplitter. Further, and returning light of the illumination light forphotographing the interference pattern may be reflected by each of thefirst optical path coupling element and the second optical path couplingelement, and guided to an image sensor of the interference photographingsystem.

In the above example aspect, each of the optical path coupling element51 and the optical path coupling element 53 is a beam splitter (e.g., ahalf mirror etc.). Further, the returning light of the illuminationlight for photographing the interference pattern may be reflected byeach of the optical path coupling element 51 and the optical pathcoupling element 53, and guided to the interference photographing camera23 corresponding to the image sensor.

According to the exemplary embodiment thus configured, the disturbanceof light when passing through a beam splitter can be avoided whilereducing the size of the p al system. Therefore, it becomes possible todetect the interference pattern generated on the cornea with highaccuracy.

The ophthalmologic apparatus according to some exemplary embodiments mayfurther include an illumination intensity changing device that changesthe intensity of the illumination light projected onto the anterior eyesegment. In the above example aspect, the variable filter 14 and theillumination intensity changing processor 130 correspond to theillumination intensity changing device.

According to the exemplary embodiment configured in this way, theophthalmologic apparatus can perform the examination with the light ofsuitable intensity. For example, the ophthalmologic apparatus can reducethe possibility that the subject closes his or her eyes due to glareduring the examination that takes a certain period of time, such as thetear film breakup time (BUT) examination. In addition, theophthalmologic apparatus can reduce a burden on the subject.

The ophthalmologic apparatus according to some exemplary embodiments mayfurther include an excitation filter that generates excitation light fora fluorescent agent administered to the anterior eye segment from theillumination light, and a barrier filter that selectively passesfluorescence emitted from the fluorescent agent that has absorbed theexcitation light. In the above example aspect, the excitation filter 13corresponds to the excitation filter, and the barrier filter 31corresponds to the barrier filter.

According to the exemplary embodiment configured in this way, thefluorescent contrast photographing of the anterior eye segment can beperformed. Therefore, the examiner can observe the state of the corneaand the state of the tears in more detail.

The ophthalmologic apparatus according to some exemplary embodiments mayinclude elements for alignment. The alignment can facilitates theexamination. Some examples of the configuration for alignment are givenbelow.

As the first example, the ophthalmologic apparatus according to someexemplary embodiments may include a projection system, a detectionsystem, and a first alignment device. The projection system isconfigured to project alignment light onto the anterior eye segmentalong a direction non-parallel to the optical axis of the optical pathfrom the first optical path coupling element toward the subject's eye.The detection system is configured to detect reflected light of thealignment light projected onto the anterior eye segment by theprojection system. The first alignment device is configured to performalignment in a direction along the optical axis, based on an output fromthe detection system.

In the above example aspect, the alignment light source 61, the lens 42,and the lens 41 correspond to the projection system. Furthermore, thelens 41, the lens 42, and the image sensor 62 correspond to thedetection system. In addition, the unit movement mechanism 70 and thealignment processor 140 correspond to the first alignment device. The Zalignment is carried out using these elements.

In the first example, the projection system may include an alignmentlight source that outputs the alignment light. Further, the detectionsystem may include an image sensor that detects the reflected light ofthe alignment light. In addition, the alignment light source and theimage sensor may be disposed in positions on the opposite side of thesubject's eye with respect to the first optical path coupling element.

In the above example aspect, the alignment light source 61 correspondsto the alignment light source and the image sensor 62 corresponds to theimage sensor. Further, the alignment light source 61 and the imagesensor 62 are disposed in positions on the opposite side of thesubject's eye E with respect to the optical path coupling element 51,that is, on the side of the anterior eye segment photographing system30. The optical path coupling element 51 is formed with a notch, anaperture, a light transmitting part, or the like, and the light may passthrough the optical path coupling element 51 via the notch, theaperture, the light transmitting part, or the like.

As the second example, the ophthalmologic apparatus according to someexemplary embodiments may further include a second alignment device. Thesecond alignment device is configured to perform alignment in adirection perpendicular to the optical axis of the optical path from thefirst optical path coupling element toward the subject's eye, based onan anterior eye segment image acquired by the anterior eye segmentphotographing system.

In the above example aspect, the unit movement mechanism 70 and thealignment processor 140 correspond to the second alignment device. TheXY alignment is carried out using these elements.

As the third example, the ophthalmologic apparatus according to someexemplary embodiments includes two or more photographing devices and athird alignment device. The two or more photographing devices areconfigured to photograph the anterior eye segment from directionsdifferent from each other. The third alignment device is configured toperform three dimensional alignment based on two or more photographedimages respectively acquired by the two or more photographing devices.

In the above example aspect, the two anterior eye segment cameras 300Aand 300B correspond to the two or more photographing devices, and theunit movement mechanism 70 and the alignment processor 140A correspondto the third alignment device. The three dimensional alignment (the XYZalignment) is carried out using these elements.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

In this specification, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

Singular forms in this specification are intended to include the pluralforms as well, unless the context clearly indicates otherwise.

The terms “comprises” and/or “comprising”, when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

In this specification, ordinal numbers (e.g., first and second) used todescribe elements are only intended to distinguish one element fromanother element.

What is claimed is:
 1. An ophthalmologic apparatus comprising: anillumination system that projects illumination light output from a lightsource onto an anterior eye segment of a subject's eye; an interferencephotographing system for photographing an interference pattern formed ona cornea by the illumination light; an anterior eye segmentphotographing system for photographing the anterior eye segment ontowhich the illumination light is being projected; a first optical pathcoupling element that couples an optical path of the interferencephotographing system and an optical path of the anterior eye segmentphotographing system with one another; and a controller that controls adisplay device to display an interference image acquired by theinterference photographing system over an anterior eye segment imageacquired by the anterior eye segment photographing system.
 2. Theophthalmologic apparatus of claim 1, further comprising: a first lensgroup disposed in a position between the subject's eye and the firstoptical path coupling element; and a second lens group disposed in aposition on an opposite side of the subject's eye with respect to thefirst optical path coupling element, wherein a combination of the firstlens group and the second lens group functions as an objective lens ofthe interference photographing system, and the first lens groupfunctions as an objective lens of the anterior eye segment photographingsystem.
 3. The ophthalmologic apparatus of claim 2, wherein a lenslocated closest to the first optical path coupling element among lensesincluded in the anterior eye segment photographing system is disposed ata focal position of the first lens group or in a vicinity thereof. 4.The ophthalmologic apparatus of claim 1, further comprising a secondoptical path coupling element that couples an optical path of theillumination system and the optical path of the interferencephotographing system with one another.
 5. The ophthalmologic apparatusof claim 4, wherein each of the first optical path coupling element andthe second optical path coupling element is a beam splitter, andreturning light of the illumination light for photographing theinterference pattern is reflected by each of the first optical pathcoupling element and the second optical path coupling element and guidedto an image sensor of the interference photographing system.
 6. Theophthalmologic apparatus of claim 1, further comprising an illuminationintensity changing device that changes an intensity of the illuminationlight projected onto the anterior eye segment.
 7. The ophthalmologicapparatus of claim 1, further comprising: an excitation filter thatgenerates excitation light for a fluorescent agent administered to theanterior eye segment from the illumination light; and a barrier filterthat selectively passes fluorescence emitted from the fluorescent agentthat has absorbed the excitation light.
 8. The ophthalmologic apparatusof claim 1, further comprising: a projection system that projectsalignment light onto the anterior eye segment along a directionnon-parallel to an optical axis of an optical path from the firstoptical path coupling element toward the subject's eye; a detectionsystem that detects reflected light of the alignment light from theanterior eye segment; and a first alignment device that performsalignment in a direction along the optical axis based on an output fromthe detection system.
 9. The ophthalmologic apparatus of claim 8,wherein the projection system comprises an alignment light source thatoutputs the alignment light, the detection system comprises an imagesensor that detects the reflected light, and the alignment light sourceand the image sensor are disposed in positions on an opposite side ofthe subject's eye with respect to the first optical path couplingelement.
 10. The ophthalmologic apparatus of claim 1, further comprisinga second alignment device that performs alignment in a directionperpendicular to the optical axis of the optical path from the firstoptical path coupling element toward the subject's eye, based on ananterior eye segment image acquired by the anterior eye segmentphotographing system.
 11. The ophthalmologic apparatus of claim 1,further comprising: two or more photographing devices that photographthe anterior eye segment from directions different from each other, anda third alignment device that performs three dimensional alignment basedon two or more photographed images respectively acquired by the two ormore photographing devices.